Dental instrument



Jan. 29, 1963 BALAMUTH ET Al. 3,075,288

DENTAL INSTRUMENT 2 Sheets-Sheet 1 Filed Dec. 24, 1954 57M hid/m4 A M ATTORNEYS 2 Sheets-Sheet 2 ATTORNEYS L. BALAMUTH ET AI.

DENTAL INSTRUMENT.

Jan. 29, 1963 Filed Dec. 24, 1954 3,075,288 DENTAL INSTRUMENT V Lewis B'alamuth, Woodside, and Arthur Kuris, Bronx,

N.Y., assignors to Cavitron Ultrasonics, luc acorporation or New York lliiled'Dec. 24, 1954, Ser. No. 477,530 11 Claims, (Cl.- 32-58) The present invention relates to sonic and" ultrasonic instruments particularly designed for use'bythe dental and surgical profession. v

Sonic and ultrasonic cutting, as describedin-Bala'muth U.S. Patent No. 2,580,716, issued' January '1, 1952; is practised by the use of a toolin which high frequency longitudinal vibrationsfoiv minute amplitude are set up by an electro-mechanical transducer, for example, a magnetostrictive transducer. Abrasive, in finely divided form and suspended'in a liquid, usually wat er, is interposed between the work to be cut and the vibrating endof the tool. When pressure is applied to advance the tool into the work, the abrasive particles which are highly accelerated as a result of the vibrations at the working end of the 'tool, cut the work and produce holes or cavities therein having'cross-sectional configurations conforming to that of the tool.

Prior to the present invention the above briefly described process has been employed in industry for cutting or drilling hard and/or brittle materials such as carbides, crystalline gem stones, germanium, ceramics and hardened tool steels. The specific ultrasonic devices heretofore in use were not specifically designed for cutting or drilling teeth. As a result of study of-dentistsdequirements for ready use of their professional skill, we have developed a dental instrument which operates on the principles disclosed in said Balarnuth patent and which differs radically from the conventional dental drill. The new instrument is substantially painless and entirely harmless to the patient; it utilizes the previously acquiiedskilhof the dentists; it'reduces chair time on conventional operations and it can perform operations and obtain results unobtainable by conventional dental drills.

Production of a commercially practicable ultrasonic dental instrument involved "the solution of many problems such as, the mounting of the vibrator Within a hand piece Whose dimensions correspond to those of a conventional dental drill,-the provision of a'small size vibrator comprising an efiicient magnetostlrictive transducer and'tool'holder; and the provision of means for supplying electrical energy to the transducer, means'for cooling the transducer, and means for supplying cutting liquid and treating fluid to'th'e work -area-of the tool; all without restricting the manipulation of the hand piece by the operator.

In the foregoing we have briefly outlined some "of'the problems encountered and solved in the production of the new dental instrument of this invention. instrument comprises in general a hand piece substantially of the size of the conventional drill to one end f which a smalldental tool of any desired configuration-may be attached. The hand -piece comprises an open ended casing housing a vibrator which includes a magnetostrictive transducer and a tool holder or acoustical impedance transformer fixed to one end of the transducer, and which provides an acoustical transmission line between the transducer and work tool. The vibrator is mounted in the casing by means of'a ring of compressible material located in the neighbo-rhqodof a node of longitudinal'vibration of the tool holder, when compressional waves-ofthe operating frequency are generatedby the-transtfiicerjmeans' being provided for The new 3&753288 Patented Jan. 29, 1963 ice 2. preventing relative rotation between the casing and the tool holder. For'maximum amplitude of vibration of the'tool end, and for maximum transmission of working energy, the overall length of transducer, transformer and tool, is so correlated to the frequency of the electrical oscillations delivered to the transducer, that a loop of motion of the generated compressional waves will occur at or near the working end of the-tool. In other words, the overall length of transducer, tool 'holder and tool are approximately equal to an integral numberof one-half wavelengths of sound Waves in the particular materials comprisingthe transducer,

transformer and tool at the'workin'g frequency;

The'end of the'casing encompassing the transducer is 'madeto accommodate a Water inlet tube which enters into the casing through a removable plug or closure for that end of the casing-and extends for substantially'the length of the transducer. A short tube extending through the plug provides the outlet for the cooling water; The compressible mounting ring serves to prevent uncontrolled leakage of cooling water to the tool end of the casing, and permits radial expansion and contraction of the'transformer. The transducer comprises a laminated stack of magnetostr'ictive'metal sheets about which is Wound a conductor provided with a water imperviousinsulating coating. The Winding may be threaded throughaligned slots formed in the thin magnetostrictive sheets or plates which form the laminated stack. A concentric cable comprising an inner insulated conductor and an outergrounded metallic cover nters the casing through the closure plug. One end or the transducer winding is connected to the inner conductor of the cable and the other end to the grounded casing.

A capillary tube, terminating adjacent the tool end of the hand piece, is provided'for delivering warmed cutting liquid or slurry composed of a mixture of water and abrasive to the work area. Another capillary tube may be provided for delivering water or other treating liquid to the work area under the control of the operator, and which may be used for rinsing the patients mouth.

The invention also includes alternative arrangements for the delivery and control of the cutting liquid to thework area, as will be apparent as the description proceeds.

For a description of specific embodiments of theinvention, reference may be had to the accompanying drawings of which: 7

FIG. 1 is a pictorial illustration of one form ofvibratory instrument made in accordance'with this invention;

FIG. 2 is a longitudinal sectional view through'the instrument shown in FIG. 1;

FIGS; 3 and 4 are transverse sectional views on a larger scale taken on the lines 3-'3 and 4-4, respectively of FIG. 2;

FIG. 5 is a'fragmentary longitudinal sectional view showing the means for mounting the tool holder' and transducer in'the casing of the hand 'piecej FIG. 6 is a lo-ngitudinal sectionalviewthrough a dental hand piece provided with analternative arrangement for supplying a treating liquid;

FIG. 7 is anenl'arged transverse sectionalview taken on'the line'7- 7 of FIG. 6, and which furtherillustrates one' 'mean's which may be employed to control the flow of treating liquid' to' the work tool;

FIG. 8 is "a fragmentary longitudinal section of the hand piece'which incorporates a modified means for controlling the flow ofliquidto'the' work tool shown in FIG. 6 I v u u FIG.-9 is a fragmentary longitudinal section 'ot'ahand piece which includes a modified form of tool holder or smasss transformer and modified operator controlled means for supplying liquid to the work tool; and

HG. 10 is a transverse sectional View taken along line 1@:l@ of PEG. 9.

The hand supported instrument illustratedrin F168. 1, 2, 3, 4 and 5 comprises an outer casing 14 of cylindrical cross section. One end section 14 of the casing lid is of relatively small diameter and is open ended. The other end section 14" of the casing may be larger in diameter and is internally threaded at its end. A centrally apertured cap 16 is threaded to the larger end of the casing. The two end sections 14' and l are con nected by an intermediate section 14 of intermediate diameter whose length is approximately equal to that f the end section 14 of least diameter. Preferably the outer surface of the casing 14 is covered with a layer ilda of vibration absorbing material, such as rubber having closed air cells therein. Within the section lid" of larger diameter is a magnetostrictive transducer cornprising a laminated stack 18 composed of a series of relatively thin and compactly stacked plates formed of nickel or other magnetostrictive material, and an en orgizing winding 2% in surrounding relation to the laminated stack as shown in M65. 2 and 4. One end of the stack is welded or soldered to an end of a tool holder 22 shaped to Serve as an accoustical impedance transformer. The tool holder 22 extends through the intermediate section 14' and end section 14' or the casing 14 and comprises two body sections 22 and 22 of difierent cross section interconnected by a short tapered section 22a. The overall length of the tool holder or transformer 22 is substantially equal to onehalf wavelength of standing waves set up therein at the operating frequency, with the tapered section 22a which joins the body sections 22' and 22 being positioned substantially at the node of longitudinal motion of such standing waves. Magnification of amplitude of vibration is attained by virtue of a mass effect as described in the copending application of Lewis Balarnuth and Arthur Kuris, Serial No. 417,707, entitled Vibratory Machine Tool, filed March 19, 1954, Reissue Patent Re. 25,033. it is at this nodal region that the transformer or tool holder 22, with the transducer stack 18 secured thereto, is mounted within the casing 14 or the hand piece. The mounting means comprises a ring 24 of compressible material, such as rubber, which seats in an annular recess in the transformer or tool holder 22 and forms ayielding water tight seal between the casing 14 and the transformer 22 contained therein. The compressible ring 24 does not appreciably dampen radial vibrations present at the nodal region of the transformer 22 and therefore does not subject the transformer to external stresses.

T 0 avoid interference with the high frequency longitudinal vibrations set up in the tool holder or transformer 22 and tool 3% when the transducer stack 18 is energized, the dimensions of the casing 14- and tool holder 22 are such as to provide clearance therebetween. To prevent relative rotation between the tool holder 22; and casing 14, a transverse pin 26 may be inserted in aligned transverse holes in the casing 14 and tool holder 22 adjacent the nodal region 22a where the longitudinal movement is negligible. The holder 22 is provided at its end with a threaded aperture for reception or" a stud 28 carrying a work tool or dental tool 30.

A plug 32, which is held by friction within the larger end of the casing 14 and abuts the cap 16, is provided with four holes therethrough as shown in FIGS. 2 and 3. These four holes receive water inlet and outlet conduits 3d and 36, respectively, a coaxial electrical cable 33 and a capillary tubing 4%. The coaxial cable 38 comprises an outer metallic grounded cover which is conductively connected to the casing 14 through the plug 332, and an inner conductor 38' provided with an insulating water impervious coating. The insulated inner conductor 38' forms the winding 26 and is grounded at its endto the stack or to the casing. The coil 20 may be threaded through aligned slots formed in the magnetostrictive plates which compose the transducer stack 18, as in convenlional practice and as shown in FIG. 4. The diameter of the casing 14 is such that there is only small play between the transducer and the inner wall of the casing 14- Thus the transducer and tool holder 22 are centerzd and supported by the resilient O-ring 24, without addtional supporting means which could hamper vibration. Extending along the inner wall of the casing 14 adjacent the transducer is a water delivery line 42 which at one end is connected within the plug 32 to the water inlet tube 3d and terminates at its other end adjacent the juncture of the transducer stack "18 with the transformer 2 2. A short water outlet conduit 44 is carried in the plug 32 and makes connection with the outlet hose 36 therein.

The capillary tubing 4%, which connects within the plug 32 to a flexible capillary tube 41, extends through the section of casing M containing the transducer and passes out through an opening in the casing 14 located substantially at the junction between the intermediate and large diameter sections 14 and 14" thereof. Externally of the casing, tubing 459 is connected by plastic tubing 46 of nylon or the like to a short soft steel capillary terminal tube 43. The tube 43 is brazed to a steel ring 59 slid-ably supported by an Gring 52 on the small diameter body section 14' of the casing 14. The soft steel tubing 48 and the ring 59 permit the operator, while holding the hand piece in his hand, to adjust the angular and longitudinal disposition of the nozzle or tip of the terminal tube 48 with reference to the tool end. It is through the terminal tube 43, flexible capillary tubing 2-6, tubing 4% and flexible tubing 41 connected thereto within the plug 32, that cutting liquid is delivered to the work area at the Working end or" the tool 3%.

The operator manually manipulates the hand piece 6 and the tool 30 associated therewith in substantially the same manner as he would manipulate the hand piece of a rotary dental instrument.

In FIGS. 6 to 10, arrangements for delivering preheated Water to the work area are disclosed. In each of these arrangements, the water delivered to the work area is drawn from the cooling water provided for the transducer. In the embodiment of FlGS. 6 and 7 a first small metallic tube 116 is mounted on the outside of the casing 14 over the casing section 14 of lesser diameter and terminates in a nozzle 118 adjacent the tool 30. A second small metallic tube 116 terminates adjacent the plug 32 within the chamber formed by the section of the casing 14 of larger diameter. A compressible tube 12% connects the two metallic tubes 11d and 116' whose adjacent ends are cut off in planes of approximately 45 to the axis of the tubing. An expansible ring 122 of rubber or the like encircles the intermediate section 14" of the casing 14 and is positioned intermediate the interrupted ends of the tubes 11d and 11d and normally collapses the wall of the compressible connecting tubing 126) as shown in FIG. 7. When the operator moves the ring 122 longitudinally along the casing 34 in either direction, the ring 122 rides up the sloping end or" either one of the tubes 116 or 116', thereby permitting the collapsed compressible tube 120 to expand and deliver water to the nozzle 118. The wate delivered through the tubes 116 and 116' to the tool 36? is warmed by the vibration heated transducer in the chamber of casing 14-.

In FIG. 8 an alternative arrangement for controlling the passage of Water through the collapsible tube 129 is shown. In this arrangement a ring 122a of nonexpansible material encompasses the casing 14 and compressible tube 129. A compression spring 124 is interposed between the inner surface of the ring 122:: and the casing 14 at a position diametrically opposite to the collapsible tube 128. Thus when the operator presses on the ring 122a to compress the spring124, the water passage through the collapsible tube 120 will be opened.

In FIGS. 9 and 10 an internal feed of water. to the work area is illustrated. in this construction the tool holder 126 is provided with a longitudinal passage'l27 which at its inner end intersects a radial passage 128 which is normally closed by a valve plug 1% carried on the inner surface of a collar 132. A leaf spring 134 mounted within the collar 132 and bearing against the casing 14 operates to drawthe diametrically opposite valve plug 130 presented by the inner surface of the collar 132 into valve closing position. The operator, by pressure on a button 136 mounted on a pin extending through the casing wall 14 and connected to the collar 132,may move the collar 132 against the bias of the spring 134 to lift the valve plug 13% away from the passage 12% and thereby permit flow of water through the passages 128 and 127. To permit leakage of Water from the passage 127 to the work area, the threaded studand tool body of the tool'3tl used in this embodiment of the invention is provided with a longitudinal slot 138.

It will be apparent from the foregoing description that we have provided an eflicient dental instrument which differs fundamentally from dental drills heretofore in use. The new instrument does not require the operator to learn radically new tezhniques, is simple to operate and, by choice of suitable materias, can be made light to handle. The hand piece partsare relatively s'mpe to construct and assemble. For example, in the embodiment of the invention illustrated in FIG. 2, after the transducer 13 and transformer 22; have been constructed and secured together and the compressible ring 24 mounted in the groove provided therefor, the assembly may be introduced as a unit through the larger end of the casing 14 together with the plug 32 and the parts coupled thereto. The cap 16 may then be screwed into place against the plug 32. Changing from one dental tool to another can be readily effected after the tool holder 22 is thus positioned within the casing 14 and the transverse pin 26 positioned in the mating holes. Obviously a wide variety of shapes of tools can be provided to meet desired cutting operations. As the present invention is not concerned with the specific shape of any one of the tools which might be employed, no attempt has been made hereinto illustrate other than the straight tool shown in H63. 2 and 9.

It will be apparent that many changes could be made in the specific constructions illustrated in the drawings without departing from the spirit of the invention or the scope of the accompanying claims, and various circuit arrangements for producing the high frequency oscillatory current and the DC. bias current could be employed.v

It will be apparent from the foregoing description, that the specific dimensions of the hand piece will depend to a large extent upon the selected operating frequency, the lower the frequency, the greater the overall length of the handpiece; Although an operating frequency'in the upper audible range is entirely feasible, we prefer to employ higher operating frequencies not only to keep small the physical dimensions of the hand piece but also to insure quiet operation. The presently preferred operating frequency is in the order of twenty-nine kilocycles per second.

The following is claimed:

1. A dental instrument comprising a magnetostrictive transducer which includes a vibrator section formed of" magnetostrictive material and an energizing coil .in surrounding relation thereto, means for connecting said. energizing coil to a source of high frequency electrical oscillations, an acoustic transmission seciion fixed to one-end of said vibrator section, said vibrator section and transmission section extending into an open ended. casing of a size adapted to be held in and manipulated by the hand of ,an operator, a dental tool mounted on the other end of said transmission section and protruding beyond the adjacent open end of thecasing, a closure for the other end of the casing,. inlet and outlet means extending through said closure for circulating a coolant adjacent said vibrator section, support means for the transmission section and vibrator section interposed between the-inner Wall of .said casing and the transmission section and positioned substantially atthe node of motion of longitudinal waves present in said transmission-sectionwhen said coil is connected to said source, said support'means forming a seal between the transmission section and casing, and ,tubingconnected to the coolant inlet and outlet means insaid end closure.

2. An instrument comprising an elongated mechanical vibrator having an operativetool fixedto and'exte'nding from one end thereof, said vibrator having at least'a sectional length thereof formed of magnetostrictive material extending within an energizing coil to form therewith a magnetostrictive transducer adapted to engender at. the tool end mechanicaloscillations of high frequency and minute amplitude, an enclosing casing containing said energizing coil and vibrator and presenting the operative tool projecting beyond one end of the casing, a closure for the other end of the casing, means which includes a sealing element formed of resilient material for supporting the vibrator in spaced relation to the interior wall of the casing and in spaced relation to said end closure to thereby define a casing chamber between said end closure and said supporting means for the containment of a coolant, and .inlet means for admission-of coolant into said casing chamber.

3. An instrument comprising an elongated mechanical vibrator having an operative tool fixed to and extending from one end thereof, said vibrator having at least a sectional length thereof formed of magnetostrictive material extending within an energizing coil to form therewith a magnetostrictive transducer adapted to engender at the tool end mechanical oscillations of high frequency and minute amplitude, an enclosing casing containing said energizing coil and vibrator and presenting the operative toolprojecting beyond one end of the casing, a closure for the other end of the casing, means which includes a sealing element formed of resilient material for supporting the vibrator in spaced relation to the interior wall of the casing and in spaced relation to said end closure to thereby define a casing chamber between said end closure and said supporting means for the containment of a coolant, a current supply. line extending through said end closure and connected to said energizing coil, and a coolant supply line extending through said end closure for supplying coolant to said casing chamber.

4. An instrument comprising an elongated mechanical vibrator. having an operative tool fixed to and extending from one end thereof, said vibrator having at least a sectional length thereof. formed of magnetostrictive material extending within an energizing coil to form therewith a magnetostrictive transducer adapted to engender at the tool end mechanical oscillations of high frequency and minute amplitude, an enclosing casing containing said energizing coil and vibrator and presenting the operative tool projecting beyond one end of the casing, a closure for the other end' of the casing, means which includesa sealing element formed of resilient material for support* ing the vibrator in spaced relation to the interior Wall of the casing and; in spaced relation to said end closure to thereby define a sealed casing chamber between said end closure and said supporting means for the containment of a coolant, said sealing element being positioned substantially at the node of motion of longitudinal waves present in said vibrator when said coil is energized with high frequency oscillations.

5. An instrument comprising an elongated mechanical vibrator having an operative tool fixed to and extending from one end thereof, said vibrator having at-least a sectional length thereof formed of magnetostrictive material extending within an energizing coil toforrri'therewith a aovaees magnetostrictive transducer adapted to engender at the tool end mechanical oscillations of high frequency and minute amplitude, an enclosing casing containing said energizing coil and vibrator and presenting the operative tool projecting beyond one end of the casing, a closure for the other end of the casing, means which includes a sealing element formed of a resilient material for supporting the vibrator in spaced relation to the interior wall of the casing and in spaced relation to said end closure to thereby define a casing chamber between said end closure and said supporting means for the containment of a coolant, a current supply line extending through said end closure and connected to said energizing coil, a coolant supply line extending through said end closure and into said chamber for supplying coolant to said casing chamber, and a coolant dischar e line extending from said chamber through said end closure.

6. An instrument comprising an elongated mechanical vibrator having an operative tool fixed to and extending from one end thereof, said vibrator having at least a sectional length thereof formed of magnetostrictive material extending within energizing coil to form therewith a magnetostrictive transducer adapted to engender at the tool end mechanical oscillations of high frequency and minute amplitude, an enclosing casing containing said energizing coil and vibrator and presenting the operative tool projecting beyond one end of the casing, a closure for the other end of the casing, means which includes a sealing element formed of res: ent material for supporting the vibrator in spaced relation to the interior Wall of the casing and in spaced relation to said end closure to there by define a casing chamber between said end closure and said supporting means for the containment of a coolant, a current supply line extending through said end closure and connected to said energizing coil, a coolant supply line extending through said end closure and into said chamber for supplying coolant to said casing chamber, a coolant discharge line extending from said chamber through said end closure, and a feed line extending through said end closure and terminating at a point adjacent to the terminal end of said operating tool for supplying a flowable treating material to the work area, said tube having a section thereof extending th ough said chamber and in direct heat exchange relationship with the coolant supplied to said chamber.

7. An ultransonically operative dental instrument including, a magnetostrictive transducer including a vibrator section formed of magnetostrictive material and an energizing coil in surrounding relation thereto, a tool holder section secured to one end of said vibrator section, a dental tool secured to the other end of said holder section, an open ended casing surrounding said vibrator section and holder section, a resilient sealing element interposed between said casing and holder section intermediate the ends of the holder section and in the nei hborhood of a node of motion of the longitudinal vibrations generated by said transducer at the operating frequency, a closure for the tansducer end of said casing, and leads to said energizing Winding and coolant delivery and exhaust tubes extending through said end closure.

.for the other end of the Casing, means whi h includes a sealing element formed of resilient material for supporting the vibrator in spaced relation to the interior Wall or" the casing and in spaced relation to said end closure to thereby define a casing chamber between said end closure and said supporting means for the containment of a coolant, a current supply line extending through said end closure and connected to said energizing coil, a coolant supply line extending through said end closur and into said chamber for supplying coolant to said casing chamber, and a Withdrawal line tapping said chamber and terminating at a point adjacent to the terminal end of said operating tool for supplying a tempered coolant warmed by heat energy generated by said transducer to the Work area.

9. An instrument for dental and surgical use comprising an elongated mechanical vibrator having an opera tive tool fixed to and extending from one end thereof, said vobrator havin at least a sectional length thereof formed of magnetostrictive material extending Within an energizing coil to form therewith a magnetcstrictive transducer adapted to engender at the tool end mechanical oscillations of high frequency and minute amplitude, an enclosing casing containing said energizing coil and vibrator and presenting the operative tool projecting beyond one end of the casing, a closure for the other end of the casing, means which includes a sealing element formed of resilient material for supporting the Vibrator in spaced relation to the interior wall of the casing and in spaced relation to said end closure to thereby define a casing chamber between said end closure and said supporting means for the containment of a fluid treating material, a current supply line extending through said end closure and connected to said energizing coil, a treating fluid supply line extending through said end closure and said casing chamber to a point adjacent the terminal tip of said operating tool for supplying treating fluid to the work area.

10. Ultrasonic dental equipment comprising in combination, a magnetostrictive transducer including a vibrator section formed of magnetostrictive material and an energizing Winding surrounding said vibrator section, a tool holder secured at one end of said vibrator section and designed to support a dental tool at the other end thereof, an open ended casing into which said vibrator section and at least a part of said tool holder extends, a compressible sealing element interposed between said casing and holder intermediate the ends of the holder and in the neighborhood of a node of motion of the longitudinal vibrations generated by said transducer at the operating frequency, a closure cap for the transducer end of said casing having openings therethrough for leads to said energizing Winding and for liquid delivery and exhaust tubes, and a pin coupling said casing and tool holder for preventing relative rotation therebetweeu, said pin extending transversely through the casing and holder in the neighborhood of said compressible element but on the tool side thereof.

11. An ultrasonic dental hand piece comprising, a vibrator section of magnetostrictive material having an energizing coil in surrounding relation thereto and forming therewith a magnetostrictive transducer, an acoustic transmission section fixed atone end to one end of said vibrator section, said vibrator section and transmission section extending into an open ended casing of a size adapted to be held and manipulated by the hand of an operator, a dental tool fixed to the other end of the transmission section and projecting beyond the adjacent end of the casing, a closure for the other end of the casing, liquid inlet and outlet means extending through said closure for circulation of cooling liquid around said vibrator section, support means for the transmission section and vibrator section interposed between the inner Wall of said casing and the transmission section and positioned substantially at the node of motion of longitudinal waves present in the transmission section when said coil is energized with high frequency electrical oscillations, said References Cited in the file of this patent UNITED STATES PATENTS Hayes July 17, 1934 10 Henschel June 10, 1941 Page May 13, 1947 Broussard et a1 Nov. 28, 1950 Carwile Sept. 8, 1953 Vang Aug. 9, 1955 Richards Feb. 24, 1959 

1. A DENTAL INSTRUMENT COMPRISING A MAGNETOSTRICTIVE TRANSDUCER WHICH INCLUDES A VIBRATOR SECTION FORMED OF MAGNETOSTRICTIVE MATERIAL AND AN ENERGIZING COIL IN SURROUNDING RELATION THERETO, MEANS FOR CONNECTING SAID ENERGIZING COIL TO A SOURCE OF HIGH FREQUENCY ELECTRICAL OSCILLATIONS, AN ACOUSTIC TRANSMISSION SECTION FIXED TO ONE END OF SAID VIBRATOR SECTION, SAID VIBRATOR SECTION AND TRANSMISSION SECTION EXTENDING INTO AN OPEN ENDED CASING OF A SIZE ADAPTED TO BE HELD IN AND MANIPULATED BY THE HAND OF AN OPERATOR, A DENTAL TOOL MOUNTED ON THE OTHER END OF SAID TRANSMISSION SECTION AND PROTRUDING BEYOND THE ADJACENT OPEN END OF THE CASING, A CLOSURE FOR THE OTHER END OF THE CASING, INLET AND OUTLET MEANS EXTENDING THROUGH SAID CLOSURE FOR CIRCULATING A COOLANT ADJACENT SAID VIBRATOR SECTION, SUPPORT MEANS FOR THE TRANSMISSION SECTION AND VIBRATOR SECTION INTERPOSED BETWEEN THE INNER WALL OF SAID CASING AND THE TRANSMISSION SECTION AND POSITIONED SUBSTANTIALLY AT THE NODE OF MOTION OF LONGITUDINAL WAVES PRESENT IN SAID TRANSMISSION SECTION WHEN SAID COIL IS CONNECTED TO SAID SOURCE, SAID SUPPORT MEANS FORMING A SEAL BETWEEN THE TRANSMISSION SECTION AND CASING, AND TUBING CONNECTED TO THE COOLANT INLET AND OUTLET MEANS IN SAID END CLOSURE. 